Williams sealed Dallas’ first-ever opening-day loss to the Giants (in nine tries) by deciding to stay in bounds at the end of a 14-yard catch from Dak Prescott instead of heading for the sidelines.

The crucial problem with Williams’ choice: The Cowboys were out of timeouts and couldn’t get Dan Bailey on the field in time to try a 58-yard field goal before the clock ran out.

“I was just doing my best to get the team in a position to kick a field goal, but obviously I should have just followed the rules and gotten out of bounds,” Williams said.

“In my mind, I was just trying to get a first down and dive out of bounds, but it just didn’t go as planned,” Williams added. “It was just a ‘bang-bang’ moment. Now that I’ve had a chance to sit back and think on it, I should have just gone out of bounds.

Compounding Williams’ error was that the catch came in front of the Cowboys’ sideline with seemingly all of his teammates pointing him to get out of bounds.

Dallas coach Jason Garrett could barely hide his disgust at Williams’ mistake, telling reporters that his team is regularly instructed on the proper move in that situation.

“What he needed to do there was simply run out of bounds,” Garrett said. “It’s a well-practiced situation. We’ve been in that situation a lot, but his instinct took him to the inside.”

Cowboys owner Jerry Jones couldn’t resist piling on, either, blasting Williams for not doing what he has been repeatedly taught to do in that circumstance.

Jason GarrettGetty Images

“He knew to get out [of bounds], and he was coached to get out,” Jones said. “He thought he was cut off [from the sideline], and those instincts are hard to deter. But make no mistake about it — he knew and was taught to get out of bounds.”

To be fair to Williams, some replays did appear to indicate that Williams would not have had a straight or easy path to the sideline. But to not even try to do so was inexcusable to Garrett and the Cowboys.

Williams’ forgetfulness didn’t end there, either. He was on the verge of walking out of the Cowboys’ locker room without the large pair of diamond earrings he arrived in until a team official scooped them out of his locker and waved frantically for Williams to retrieve them.

“It was a poor decision on his part,” Garrett said of Williams’ massive misplay. “We talked to him about that, and he understands that. His instincts took over, and we’ll all learn from that situation.”